The overall objective of this research is to investigate the molecular and metabolic mechanisms involved in disturbed intermediary metabolism in IVA, MMA, and PA. There is mounting evidence that mitochondrial dysfunction plays a role in the pathology of these disorders. Since standard treatment for these disorders is to corect the deficiencies in intermediary metabolism through dietary and cofactor supplementation, and we submit that a better understanding of these mitochondrial disturbances will allow for improved treatments. Our novel assessment of citric acid cycle intermediates in plasma from patients with IVA, MMA, and PA has revealed distinct and disease specific patterns of metabolites. Our goal is to optimize our metabolomic approaches and introduce new genomic approaches in order to further define the metabolic and molecular pathways involved in aberrant mitochondrial metabolism We wil apply mass spectrometry (MS) techniques to create non-targeted qualitative metabolomic profiles of plasma samples from patients with MMA, PA and IVA. We will then use targeted techniques including stable isotope dilution MS to quantify metabolites of greatest interest. We expect that these metabolite profiles will help to define the complex aberrations in biochemistry underlying the pathophysiology in these diseases. These metabolite profiles also have the potential to aid in the identification of novel targets for therapeutic intervention. We will next use non-targeted and targeted metabolomic approaches to examine the differences in intermediary metabolism in sick and well patients. These differences will aid in the understanding of the changes in biochemistry leading to acute illness, as wel as the identification of novel targets for therapeutic intervention during intercurrent illness. We then ill explore the underlying biochemical basis of impaired energy metabolism in mouse models of MMA via plasma specific metabolic profiling. Metabolic profiling in the plasma of mice with MMA will reveal similarities and differences in species specific biochemical response to disease. In the later phase of investigation we will determine the molecular mediators of intermediary mitochondrial metabolism in liver tissue derived from mice affected with MMA using mRNA-seq transcriptome analysis. These studies will complement our metabolomic work, and understanding of the functions of proteins encoded by these genes will provide insights into the mechanisms underlying disturbed biochemistry. PUBLIC HEALTH RELEVANCE: We propose to investigate the underlying biochemical mechanisms of Isovaleric Acidemia, Propionic Acidemia, and Methylmalonic Acidemia. These disorders, though rare, compromise a large fraction of inpatient metabolic genetics services, are difficult to treat, and cause significant morbidity and mortality. We propose to use metabolomic techniques in mass spectrometry and mRNA-seq transcriptome analysis to better understand the underlying biochemistry in these disorders, with the goal of discovering new targets for treatment.